Require "link proto" argument value to be within range.

Require "link proto" argument value to be within range.

pcap_compile() fails to reject invalid link-layer protocol numbers, for
example:

$ filtertest EN10MB 'link proto 0x12345678'
(000) ldh      [12]
(001) jeq      #0x12345678      jt 2	jf 3
(002) ret      #262144
(003) ret      #0
(loads a 16-bit value and compares it with a 32-bit value)

$ filtertest EN10MB 'link proto 1200'
(000) ldh      [12]
(001) jgt      #0x5dc           jt 5	jf 2
(002) ldb      [14]
(003) jeq      #0x4b0           jt 4	jf 5
(004) ret      #262144
(005) ret      #0
(loads an 8-bit value and compares it with a 16-bit value)

Fixing this failure to fail requires well more than one check because
the valid range and values of a protocol number are specific to the DLT
and/or the protocol, also in some cases there is a mapping between
different protocols.  Add a reject filter test for every new check.